1. Field of the Invention
The present invention relates to a semiconductor integrated circuit device and, more particularly, to a semiconductor integrated circuit device having a nonvolatile semiconductor memory and an information storage method therefor.
2. Description of the Related Art
Recently, electronic devices such as cell phones and IC cards have widely spread. These electronic devices require a nonvolatile semiconductor memory as a recording medium (memory unit). At present, a flash memory is generally used as a nonvolatile semiconductor memory. The flash memory is not suitable in terms of the write speed and random accessibility. For this reason, an SRAM or DRAM is often used as a cash memory together with the flash memory. In this case, the memory unit incorporated in one electronic device is formed by a plurality of types of devices.
A ferroelectric semiconductor memory as one of nonvolatile semiconductor memories has a higher write speed than that of the flash memory, and enables random access. The ferroelectric semiconductor memory, therefore, receives a great deal of attention as a device which allows forming a memory unit incorporated in one electronic device by one type of device. The ferroelectric semiconductor memory is described in, e.g., reference 1: reference 1: U.S. Pat. No. 6,320,782